The present invention concerns a sprayer for coating articles with several sprayguns accommodated in an essentially solid-walled spraybooth, wherein a conveyor with a motor-revolved belt conveys the articles through the spraybooth, and a belt-wiping assembly rests against and extends across the belt and wipes its surface clean.
The articles being coated are distributed along the upper strand of the conveyor belt and transported continuously through the spraybooth. The belt is horizontal at least at this point. The articles are coated with lacquer or enamel by the sprayguns. Some of the coating "oversprays," landing on areas of the belt not masked by the articles. The surface of the belt has to be cleaned as soon as each article is removed. It is simultaneously possible to recover the excess coating.
European Patent 0 425 969 A1 describes equipment for cleaning the belt in a coating sprayer of the genus of interest herein. The equipment is positioned in the vicinity of and below the downstream belt-reversing roller. It basically consists of a cylindrical scraper that rotates more rapidly than the roller and in the opposite direction. The axis of the scraper parallels that of the roller. The scraper scrapes off any coating that lands on the belt. The scraper is fairly remote from where the articles leave the booth. This is because thorough cleaning of the belt requires additional equipment for the lower strand as it travels back upstream. The additional equipment occupies additional space. The upper strand must be lengthened by that measure because all the cleaning equipment must be outside the booth. The coating has more time to dry on the belt. The more rapid-drying the coating is and the finer the droplets are, the more difficult it is to scrape off and recover. The downstream equipment must be more powerful and consume more solvent. Another drawback to the known equipment is that, being under the belt, it is time-consuming to maintain. This drawback has to be encountered by a complicated approach involving lowering the equipment below the coating point and removing it at one side to make it accessible for daily cleaning and maintenance. Since the contact between the scraper and the belt is only linear, a single scraping will be insufficient, and the belt will have to be recleaned once or twice. Since the coating scraped off by the scraper flows over the total width of the belt and into a gutter along the side, it must be kept from drying by being repeatedly advanced by a pusher. This approach considerably complicates the overall equipment.
Also known are systems with stationary wipers that extend across the belt. A streak of coating is allowed to form on belts that are then removed at an appropriate point.
One drawback to this very simple solution is that the coating clogs up upstream of the wiper when the belt is moving slowly. Another is that solid particles adhere between the wiper and the belt, scratching the surface.
The coating, but not the scratches, can be prevented from clogging by accelerating the belt. Again, the befit can be accelerated only when there is another conveyor for the intercepted coating. This equipment is accordingly complicated and uses too much solvent.